Reception system



March 30., 1937. R. c. CURTIS RECEPTION SYSTEM 3 Sheets-Sheet l Filed June 12, 1934 .m t Wm ME E V mE m m 1 R ATTORNEY March 30, 1937. Q -n5 2,075,181

RECEPTION SYSTEM Filed June 12, 1934 3 Sheets-Sheet 2 INVENTOR Richard E. Eurlis ATTORNEY March 30, 1937.

R. C. CURTI$ RECEPTION SYSTEM 3 Sheets-Sheet 3 Filed June 12, 1954 BEE 5/59 IEU IE5 IBD FREUUENCY lN KILUDIELES INVENTOR Rlcharfl E. [I'urhs ATTORNEY Patented Mar. 30, 1937 UNITED STATES izsis si RECEPTION SYSTEM Richard C. Curtis, East Orange, N. .L, assignor to Wired Radio, Inc., New York, N. Y., a corpora.-

tion of Delaware Application June 12, 1934, Serial No. 730,211

6 Claims.

My invention. pertains in general to radio receiving systems and specifically relates to a universal receiver for receiving programs under varying conditions.

One of the objects of my invention consists in providing a radio receiving system having means for effecting the reception of signals from differently characterized sources.

Another object comprises providing a receiving system having means for improving the quality of reproduction by having a plural resonance accentuation of the response at certain frequencies.

A further object comprises providing a filter system of the inductively coupled type in which variation offrequency band width can be accomplished without the aid of switches or like devices.

A further object consists in providing a receiving system in which a characteristic frequency reception curve having staggered or an odd number of resonance peaks is varied in width by commonly mechanicallyv moved electrical units having no conductive electrical connection with the other circuits in the system.

These and other objects will be apparent from the following, reference being had to the accompanying drawings in which like reference numerals designate corresponding parts throughout and in which:

Fig. 1 is a schematic representation of the circuit system employed in my invention;

Fig, 2 is a representation of one embodiment of the mechanical structure employed in part of my receiving system;

Fig. 3 is a horizontal sectional view along the line 33 of Fig. 2;

Fig. 4 is a horizontal sectional view along the line 44 of Fig. 2; and

Fig. 5 is a graphical representation of certain characteristics of the receiving system according to my invention.

My invention contemplates providing a radio receiving system, preferably of the superheterodyne type, in which the input and output of the intermediate frequency amplifier includes filter networks of the inductively coupled type. Within each filter, according to my invention, there is provided a circuit unit including the 5 primary of one radio frequency transformer and the secondary of another radio frequency transformer. The primary and secondary are interconnected to have special resonance characteristics and are also specially mechanically mounted 55 so that the primary and secondary coils can be moved relative to their associated windings to vary coupling effects and thereby accomplish variations in the overall frequency transmission band of frequencies being handled by the inter--. mediate frequency amplifier. The transmission characteristics of these filters are such that they simulate the effect of an odd number of resonance circuits staggered with respect to each other along the frequency spectrum. Although various odd numbers of such resonance peaks may be employed according to my invention,1I prefer, in the present embodiment, to illustrate the use of a system characterized by three such peaks,

Referring to the drawings in detail, and particularly to Fig. l, the mixer I is connected with circuit means usually to be found in a superheterodyne receiver ahead of the intermediate frequency amplifier. This circuit means connected with the mixer I includes a high frequency amplifier and high frequency reception circuits as well as the local oscillator for producing oscillations to beat with the received high.

frequencies to produce the intermediate frequencies for reception over the intermediate frequency amplifier. The output of the mixer l is directed to an input filter circuit 2 which is of the inductively coupled type and includes an inductance 3 coupled with inductance 4 and inductance 5 coupled with inductance 6. A variable capacitor 1 is in circuit with the inductance 3 while a variable capacitor 8 forms part of the circuit connections between inductances 4 and 5. Another variable capacitor 9 is connected in circuit with the inductance 6. These capacitors are of the trimmer type usually to be found in such organizations. The inductance 6 forms part of the filter output circuit which includes a terminating impedance I0 and is connected with the input of the intermediate frequency amplifier proper which includes an electron amplifier tube l2. The output of electron amplifier tube I2 is connected, with the input of the output filter circuit I! which is similar to the input filter circuit 2. The output of this filter circuit II is then connected with the usual detector and audio amplifier system 14 and thence to a reproducing loud speaker HE. A power supply I! is provided in the'iisual manner for energizing the various electron tubes as well as the loud speaker l5.

Referring to Fig. 2, the mechanical structure of a portion of the receiving system will now be considered. The inductances 3 and 6 are mounted on supporting members 22 and 23 which a e secured to a mounting member 24. A shielding element 2| extends between the coils 3 and Gas shown. Coils 3 and 6 are positioned for inductive coupling with coils 4 and 5 which are respectively mounted by supporting members 24 and 25 carried by a mounting member 21. The mounting member 21 is secured by nuts 28 to a shaft 29 rotatably mounted in the shield 2|. The capacitor 8 is mounted on the other side of the mounting member 21 while the capacitors 1 and 9 are included in a structural unit secured to the end of the shield 2|.

The entire mechanical structure thus, described is mounted within an enclosing shield 30. The

shaft 29 extends through the mounting member" 24 and is mechanically integral with a crank 3| which is connected with a reciprocative member 32 so that reciprocative forces from member 32 can be translated into rotary motion of the shaft 29. Such rotary motion causes the spatial relationship between the coils 3 and 4 and between the coils 6 and 5 to" be varied, thus varying the inductive coupling between these coils. This condition may beseen particularly in Fig. 3 in which the coils have been so rotated.

Referring back to Fig. 1, it will be seen that the reciprocative member 32' is provided for interconnecting the rotatable shafts -29 and 29a in the two filter systems on the input and output sides of the intermediate frequency amplifier tube. By such an arrangement, it is possible to vary the coupling in both filter systems in unison. Any convenient form of knob or dial can beutilized for controlling the movement of the shaft 32 in the structural arrangement of the radio receiver. .-Referring to Fig. 5, consideration will now be given to the electrical characteristics of the. radio receiver of my invention. The curves X, Y, and

Z are a family showing the transmission frequency characteristic of my radio receiving system for difierent degrees of coupling produced by different rotative spatial relationship of the coils 4 and 5 in the filter 2 and filter IL Re- U ferring first to curve Z, it will beseen from the curve that the frequency band width here is quite wide, while the frequency band width of curve X is relatively narrow, the curve Y being intermediate such widths. The curve Z represents -close. spatial relationship of the induct.

ance while the curve X represents the opposite. Thus, when it is desired to receive a narrow band offrequencies for program reception purposes, the shaft 32 may be moved tovarythespatial relationship of the coils 4 and 5 with respect to their associated coils so that the frequency transmission of the filter assumes a characteristic such as represented by the curve X.- On the other hand, to obtain a wider band of frequencies, the spatial relationship of the coils may be adjusted to obtain a characteristicrepresented by the curve Z.";-It is an especialfeature that the mechanical structure of my invention makes 'it' possible to maintain the filter circuits as a structural unity with. the variable means enclosed as a single-moving unit without any'physi- 'calor conductive connection with the rest of the filter circuit, thus avoiding the use of movable 'contactors and inductance taps and the like.

It will be seen that the curve. Z has substantially three resonance'peaks to the. points Z fZi, and Z0, while the other curves X and Y have "similar resonance peaks butnot quiteso pronounced due to the narrower width of these bands. It is known in the artthat fi er circuits can be adjusted to achieve certain resonance characteristics and in accordance with my invention the filter circuits in my system are and of the side bands corresponding to modulation frequency at around 2300 to 3000 cycles tends to compensate for the increase in resonance which is usually present in loud speakers at these frequencies. The speaker I 5- has such a resonance characteristic. Another feature is that the carrier is not attenuated with respect to the side band frequencies and so does not tend to produce distortion and demodulation at high percentages of modulation.

For certain purposes, in accordance with the principles of my invention, the terminating impedances l0 and Illa of the filter systems 2 and Il may be adjusted in value as indicated by the arrows in Fig. 1. The relative amplitude of the resonance peaks is a function of the terminating impedances. In accordance with my'invention, therefore, the values of the terminating impedance for each filter system are made variable so that a proportionality can be maintained between the reactance values in eachfllter cu:

cuit and the respective value of terminating impedance. It should also. be noted that the three resonance peaks may be made to vanish by using It will now be apparent that I have provided a novel form of receiving organization'which' is directed to both improvements in electrical rea suitably 'low value of terminating impedance.

What I claim as new and desire to secure by Letters Patent of the United States is:

1-. In anelectrical filter system, a selection circuit comprising at least two resonant sections a and including an intermediary circuit comprising reactive elements for passing frequencies within a predetermined band, saidintermediary circuit being coupled with adjacent sections of said selection circuit solely by reactive or non-conductive coupling of said reactive elements in said intermediary circuit, and mechanical means for mechanically varying the spatial relationship of said reactive elements of said intermediary circuit as a 'unit with respect tothe remainder of said selection circuit for effecting a variation in' the frequency band width characteristics of said selection circuit asa whole, and an electrostatic shieldingextending between said sections of said selection circuit. 7 i

. 2.:The combination in accordancewith claim 1 inlwhich said reactive coupling is entirely induce tive, and in which said selection circuit includes:

inductances, and said intermediary circuit includes inductances coupled with said first men-.5.

tioned inductances, said mechanical means comprising means for relatively moving said inductances.

3. In an electrical filter system, a selection circuit comprising at least two resonant sections and including an intermediary circuit comprising reactive elements for passing frequencies within a predetermined band, said intermediary circuit being coupled with adjacent sections of said selection circuit solely by inductive coupling, said selection circuit including inductances and said intermediary circuit including inductances coupled with said first-mentioned inductances, and mechanical means for mechanically varying the spatial relationship of theinductances of said intermediary circuit as a unit with respect to the remainder of said selection circuit for effecting a variation in the frequency band width characteristics of said selection circuit as a whole, said 0 mechanical means comprising a unitary structure tial relationship of said second mentioned inductances with respect to said first mentioned inductances.

5. The filter system in accordance with claim 3 in which said selectioncircuit as a whole has a frequency transmission response including an odd number of resonance peaks.

6. In a radio receiving system, a plurality of selection circuits each having an intermediary band-pass filter circuit coupled with its respective selection circuit only by reactive coupling,

mechanical means for moving'said intermediary circuits as a whole in unison for changing their frequency band Width characteristics, and means for electrostatically shielding different parts of said intermediary circuit from each other.

RICHARD C. CURTIS. 

